Why are yawns so contagious?

Yawning, it’s very strange when you think about it, isn’t it? Opening that mouth nice and wide to gulp down some air like a goldfish. Actually, a goldfish would be gulping down water wouldn’t it. Although that does have oxygen dissolved in it. Anyway, it’s not important. Although every goldfish is important, you keep on swimming mate. Reach for the skies. Waters? I don’t know.

There have been a number of proposed causes of yawning – at least 20 psychological reasons have been proposed over the years - many of which you’ve probably heard of:

- When one’s blood contains comparatively high levels of carbon dioxide, so you yawn to gain oxygen (unproven – and yawning may in fact reduce oxygen intake compared to normal respiration)

- Yawning, especially contagious yawning (that is, responding to others’ yawns with a yawn of your own), as a way of keeping an animal, or group of animals, alert, in readiness to deal with predators

- As a herd instinct, to synchronise sleeps and moods, or to indicate empathy

- Nervousness, in a similar way to altertness, often indicates the perception of an impending need for action

- Yawning as a method of controlling the brain’s temperature

However, what’s beyond doubt is that some yawning is contagious, and now scientists think they know why.

A team from the University of Nottingham found that yawns are triggered in the primary motor cortex, a part of the brain responsible for motor function. Contagious yawning is a form of echophenomena; that is, the automatic imitation of someone else’s words or actions.

The study, published in Current Biology, saw the team monitor 36 volunteers while they watched other people yawning. Some were told that it was fine to yawn, while others were told to try not to.

They found that the urge to yawn was controlled by the ‘excitability’ of each person’s primary motor cortex. They used external transcranial magnetic stimulation (TMS) to increase people’s ‘excitability’ which, in turn, increased their likelihood to succumb to contagious yawns, showing that this particular part of the brain was the one responsible for it.

Georgina Jackson, professor of cognitive neuropsychology, said the finding could be useful in understanding other conditions that are related to the primary motor cortex. "In Tourette's, if we could reduce the excitability we might reduce the tics, and that's what we are working on."

Prof Stephen Jackson added: "If we can understand how alterations in cortical excitability give rise to neural disorders we can potentially reverse them. We are looking for potential non-drug, personalised treatments, using TMS that might be effective in modulating imbalances in the brain networks."

Dr Andrew Gallup, a psychologist at SUNY Polytechnic Institute, said: "We still know relatively little about why we yawn. Various studies have proposed links between contagious yawning and empathy, yet the research supporting this connection is mixed and inconsistent. The current findings provide further evidence that yawn contagion may be unrelated to empathic processing."

Now, did you make it this far without yawning? Well, given that, aside from in contagious situations, yawning most often occurs immediately before and after sleep and during tedious activities, if your answer is ‘no’, that means that this article was not tedious.

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Dave Fawbert

ShortList.com staff writer Dave’s primary passions are pop, prose, punning and power ballads (and alliteration). A lower division football enthusiast and long-suffering cricket fan, he is one of only 110 people followed on Twitter by Chas Hodges from Chas ‘n’ Dave. Follow Dave on Twitter like Chas: @davefawbert